The TT was chassis only from the factory. So the lamp equipment was bolted on the rear frame cross member for shipping to the dealer. Once a truck body, bed, supplied by outside builders was installed, the kerosene oil side lamps were placed on the cowl, and the oil tail lamp would be mounted to the rear of the body on the driver's side.
That tail lamp has large red lens out rear, and small clear lens on the right to shine on the license tag.